Next-generation computer technologies will require ultra-high-density data storage devices and quantum computing based on isolated spin-carriers, a field known as molecular spintronics. Single-molecule magnets (SMMs) have shown great potential for such applications. SMMs are a class of metalorganic compounds that can be magnetized in a magnetic field and exhibit magnetic behavior after the magnetic field is removed. The molecules possess intrinsic angular momentum, or spin, this is directional (either up or down). Their unique magnetic properties enable SMMs to be used in spintronics for switching from total spin up to total spin down at the molecular level, and therefore each molecule can be used as a magnetic bit of information.
The combination of a large spin ground state and high axial magnetic anisotropy in SMMs results in a barrier for the spin reversal, and therefore, the observation of slow magnetization relaxation rates below a threshold temperature value, attributed to purely molecular origin rather than long-range ordering. These characteristics enable the smallest data storage element to be as tiny as a single molecule, which would represent a breakthrough from the empirical Kryder's law, predicting a doubling of the data storage density every 13 months. The current maximum density to date is approximately 200 Gbit cm−2, whereas the upper limit by using single molecules is predicted to be 30 Tbit cm−2.
Practical applications of SMMs, however, require their organization into 2D or 3D networks to allow for read-and-write processes, which is a challenge given that SMM molecules often decompose under conditions required to obtain ordered arrays. For example, they need to be protected from the environment to retain their unique magnetic properties.
In general, lithographic techniques are well-adapted to the goal of isolating nanostructures of a few hundred molecules, but to attain the ultimate density one would have to rely on self-assembly processes of these molecules. Several approaches to the nanostructuring of SMMs have been analyzed, including association on surfaces, as well as incorporation into carbon-nanotubes and meso-porous silicas. In each instance, the nanostructures are restricted to a more short-range order and raise questions regarding stability and processability.
Similar to SMMs, single-chain magnets (SCMs) have shown potential for spintronics and other applications. SCMs are a class of one-dimensional polymeric coordination compounds with slow relaxation of the magnetization and magnetic hysteresis. SCMs typically have a large uniaxial magnetic anisotropy and strong intrachain interactions. For applications where two- or three-dimensional organization is undesirable, the chains are sufficiently isolated to prevent such organization. However, the isolation and organization of SCMs is still a subject of intense study, and there is a continued need for methods and systems that eliminate, prevent, and/or reduce inter-chain interactions among SCMs.
Accordingly, there is a continued need for controlled long-range organization of molecular magnets in different dimensionality architectures while remaining in a protected chemical environment.